Some commonly used switch assemblies have little or no bearing surface to insure even, on-axis/linear motion during actuation. When actuated with an off-center force, the key can tip off-axis and one side or corner will move noticeably much more than the rest of the key. This is known as key "diving" or tipping. Resultant forces on other related switch components may also be off center, friction often occurs as a result of mechanical interference and potential binding exists. Variations in the actuation force required to activate the contact switch are dependent upon the degree of tipping. In cases where the surrounding panel allows enough key movement and the panel design doesn't correct it, the key can actually get lodged under the front panel/housing during key diving.
Existing switches that have support for key movement are typically discrete units encased in an external housing. That housing enhances linear motion through external support. Due to the complexity of the external housing for such keys, manufacturing costs can be high. Additionally, device designs with dense populations of switches are more difficult, because more space may be required for all the external housings and related mounting requirements
Keys that have such unsupported motion can also create challenges for controlling light transmission through the switch and light leakage around the edges. One version of known technology has the light source on the circuit board at the same level as the switch. The switch contact can be an obstruction to the light path because the light sources are typically mounted off center from the key, next to the circuit board mounted switch. This causes unique manufacturing challenges as the light sources have to be very accurately aligned in order to direct an adequate amount of light past the switch and into the light transmission area of the key. Additionally this approach requires more area on the circuit board due to the placement of the mentioned components.
Yet other technology has the light within the key but connected to flexible circuitry to allow for key movement in relation to the switchboard. The lighting and switch circuitry in this design are both stationary in relation to key movement, thereby eliminating failures of flexible conductors due to fatigue or vibration.